<三>使用类模板实现STL Vector

使用类模板简单实现STL Vector

#include <iostream>
using namespace std;

template<typename T>
class MyVector {


public:

//构造函数
MyVector<T>(int size = 10) {
	T * _tep = new T[size]();
	first = _tep;
	last = _tep;
	end = first + size;//
	cout << "构建Vector，首地址" << first << endl;
}

//拷贝构造
MyVector<T>(const MyVector<T> & _src) {
	
	//对方vector是为空
	if (_src.Empty()) {
		int srcVectorySize = _src.getVectorSize();
		T * _tep = new T[srcVectorySize]();
		first = _tep;
		last = _tep;
		end = first + srcVectorySize;//
		cout << "拷贝构造构建Vector,空拷贝" << endl;
	}
	else {

		int srcVectorySize = _src.getVectorSize();
		T * _tep = new T[srcVectorySize]();
		first    = _tep;
		last     = _tep;
		end      = first + srcVectorySize;//
		T *      _srcVectorElementPoint = _src.first;
		while (_srcVectorElementPoint < _src.last) {
			*_tep = *_srcVectorElementPoint;
			_tep++;
			
			_srcVectorElementPoint++;
		}//end
		last=_tep;
		cout << "拷贝构造构建Vector" << endl;
	}

}

//赋值函数
MyVector<T> & operator=(const MyVector<T> & _src) 
{
	//避免重复
	if (this == &_src) { return *this; }

	//释放现有堆上资源空间
	if (this->Empty() == false) {
		delete[]first;
		first = nullptr;
		last = nullptr;
		end = nullptr;
	}

	int srcVectorySize = _src.getVectorSize();
	T * _tep = new T[srcVectorySize]();
	first = _tep;
	last = _tep;
	end = first + srcVectorySize;//
	T *      _srcVectorElementPoint = _src.first;
	while (_srcVectorElementPoint < _src.last) {
		*_tep = *_srcVectorElementPoint;
		_tep++;
		_srcVectorElementPoint++;
	}//end
	last = _tep;
	cout << "赋值函数构建Vector" << endl;
}

//析构函数
~MyVector<T>() {
	if (Empty() == false) {
		delete[]first;
		first = nullptr;
		last  = nullptr;
		end   = nullptr;
		cout << "析构Vector,堆地址"<<first << endl;
	}

}

//添加值,返回指向当前元素的指针,返回为 const * 不允许修改
const T * pushBack(const T & _srcValue) {
	
	//满空间,两倍扩容
	if (Full()) {
		Expend();
	}
	*last = _srcValue;
	last++;
	cout << "Vector添加元素,元素地址" << last << endl;

    return last;

}


void popBack(){
     this->last--;
}

//获取指定下标的值
T getValue(int index) const {
	if (index<0) { return *first; }
	if (index > this->getVectorSize()) { return *(last-1); }
	int flag = 0;
	T  *elementPoint = first;
	while (flag < index) {
		elementPoint++;
		flag++;
	}
	cout << "获取Vector元素值,元素地址" << elementPoint <<"元素值"<< *elementPoint << endl;
	return *elementPoint;	
}

//编辑指定下标元素的值,返回当前节点的指针 不允许通过返回指针修改
const T * eidtValue(int index,const T & _value) {
	
	if (index > this->getVectorSize() || index<0) { return nullptr; }
	int flag = 0;
	T  *elementPoint = first;
	while (flag < index) {
		elementPoint++;
		flag++;
	}
	*elementPoint = _value;
	cout << "编辑Vector元素值,元素地址" << elementPoint << "元素值" << *elementPoint << endl;
	return elementPoint;
}

//判断是否为空
bool Empty() const {
	if (first == last) { return true; }
	return false;
}
//判断空间是否满
bool Full() const{
	if (last == end) { return true; }
	return false;
}

int getVectorSize() const {
	return this->end - this->first;
}

void printVector() const {


	cout << "打印数组元素" << endl;
	T  *elementPoint = first;
	int index = 0;
	
	while (elementPoint < last)
	{	
		cout.precision(4);
		cout << "[" << index << "]=" << (*elementPoint) <<"该元素地址="<< elementPoint << endl;
		elementPoint++;
		index++;
	}
}




private:
	T * first;
	T * last;
	T * end;

	//两倍扩容
	void Expend() {

		int size = this->getVectorSize();
		
		int newSize  = size * 2;
		T  *newFirst = new T[newSize];
		T  *newLast  = newFirst;
		T  *newEnd   = newFirst + newSize;
		const T  *srcElementPoint = this->first;
		while (srcElementPoint < this->last) {
			*newLast = *srcElementPoint;
			newLast++;
			srcElementPoint++;
		}

		//释放原有空间
		delete[]first;
		first = nullptr;
		last = nullptr;
		end = nullptr;

		first = newFirst;
		last = newLast;
		end = newEnd;

		cout << "两倍扩容新堆内存地址"<< first << endl;
	}



};




int main() {

	MyVector<int> v1 (6) ;

	v1.pushBack(10);
	v1.pushBack(9);
	v1.pushBack(8);
	v1.pushBack(7);
	v1.pushBack(6);
	v1.pushBack(5);


	v1.printVector();
	v1.pushBack(4);
	v1.printVector();

	v1.eidtValue(2, 100);
	v1.printVector();

	int getValue = v1.getValue(3);

	cout << "getValue =" << getValue << endl;

	MyVector<int> v2 = v1;

	v2.printVector();


	MyVector<int> v3(10);
	v3 = v1;
	v3.printVector();
	system("pause");

	return 1;
}